When you say you 'shut the dumpvalve off ' do you mean you removed it?? If you did what dump valve did you put in its place?

The DV24 is a atmos dump valve and this in its own can cause stalling. The best thing you could is put the original dump valve (recirc dump valve) back on and the remove the battery for 15mins. After that start the engine with the AC and Headlights on for 10 mins and then go for a long run including around town and open road. This will reset the ecu and it will start learning again.

The RS is meant to run with a recirculating dump valve and quite a few have had a lot of problems with Atmos dump valves.